动态扰动下顶板块体失稳冒落研究综述

Review of unstable falling of roof rock blocks under dynamic disturbance

巷道、采场等地下开挖空间周边围岩的次生结构面发育,岩体极易被切割成多个独立岩块,并在准静态地应力或外界动力扰动作用下发生滑动冒落.针对准静态条件下的顶板失稳冒落问题,研究的重点在于结构面的扩展分析以及块体系统的受力平衡条件分析.对于动态扰动条件下的顶板岩块滑动失稳问题,不仅涉及到应力波促进下的裂隙扩展问题,还与块体系统中应力波的传播规律和应力波影响下岩块动态受力条件有关.本文分别从静态条件下与动态扰动条件下两个方面总结了顶板岩块稳定性相关研究.目前针对静态条件下的顶板块体稳定性研究已经形成了诸多较为成熟的理论体系;而对于动态扰动条件下的块体稳定性的研究主要还是集中于块体系统内部应力波传播过程的分析,忽略了对顶板岩体受扰过程中裂隙扩展和应力失衡的分析.因此,针对顶板岩块动态失稳问题的研究尚不能揭示冒落机理,而该研究的难点在于“揭示动态扰动诱发块体失稳的本质机理”.最后,介绍了课题组针对动态扰动下顶板块体滑动失稳问题开展的一系列实验与数值模拟研究,揭示了不同方向动态扰动作用诱发顶板块体滑动失稳的机理,为地下矿山冒顶灾害的防控提供一定的理论参考.

Roof caving has been the main threat to the safety of underground mining,in which the caving of roof rock blocks is particularly concerning.The secondary structural planes of surrounding rocks around underground excavations,such as roadways and stopes,are developed.The rock mass is prone to break into several independent blocks,and these rock blocks may slide and fall under the action of static in-situ stress or external dynamic disturbances.Under quasistatic stress conditions,the instability and collapse of roof rock blocks are mainly caused by structural plane extensions and changes in the stress balance condition of the rock block system.However,under external dynamic disturbances,the sliding process and instability of roof rock blocks are associated with the development of fractures triggered by stress waves.Further,they are affected by the variation of stress balance conditions of the rock block system and the transmission of stress waves in the block system.This paper summarized the existing studies on roof rock block stability under quasistatic and dynamic disturbance conditions.Previous studies have proposed relatively mature theoretical systems for the stability analysis of roof rock blocks under static or quasistatic situations.However,a majority of the studies on rock block stability under an external dynamic disturbance condition examine stress wave propagation in a rock block system while overlooking the analysis of the crack development mechanism and dynamic variation in stress balance conditions.Therefore,further research is necessary to reveal the caving mechanism of roof rock blocks triggered by a dynamic disturbance.By summarizing relevant work,the difficulties encountered in the study of roof rock block caving under a dynamic disturbance are discussed.The key scientific problem is to uncover the fundamental mechanism behind roof rock block instability induced by a dynamic disturbance.Finally,a series of experimental and numerical simulations conducted on the sliding and instability of roof rock blocks under a dynamic disturbance revealed clear differences in the mechanism of the sliding instability of roof blocks due to dynamic disturbances in different directions.The reduction in friction between the blocks is the fundamental cause of the key block sliding under a lateral disturbance,while the sliding of the rock blocks under a vertical disturbance is mainly driven by the dynamic load.This finding can provide a theoretical reference for preventing and controlling roof caving in underground mines.